Entering Data

New data can be entered, or existing data modified, in the File → Edit Data menu, which opens the Data Input Form, and displays a table for data entry and manual alteration.

CFTool operates in two modes; Data mode and Project mode.

Data mode saves simple text files as columns of data, and this is the default startup mode. In this mode, whether you use “Save Data” or “Save Data As”, the data entry window always saves a text file to disk before returning you to the main plot window, unless you cancel the operation or close the edit window. Once the values have been entered, pressing “Save Data” will write the data to a text file, and, if you are entering new data, you will be asked to name the file, or else the currently active text file will be updated and saved. The new or modified data will then be plotted in the main window. “Save Data As” simply writes the data to a new text file, leaving any existing file unchanged and then plots this new file to the main window

You enter project mode by saving the current graph using “Save Project” in the File menu, or by opening an existing project. Project files contain the raw data, as well as formatting information, any fit that you used and other modifications. Saving a new project does not delete the original data text file, both are retained. After that, modifications to the project will only be saved to the project file. In project mode, the Data Input Form is used to modify the project data, and pressing “Save Data” will update the project but not save the data to disk. Saving the project can only be done in the File menu. In project mode, pressing “Save Data As” will create a new text file and close the open project file without modification, retaining both files, and putting you back in data mode.

If you make changes to the table that you then wish to discard, simply close the window with the X in the top toolbar.

CFTool’s Data Input Form includes an interactive spreadsheet table with smart editing, range fills, and simple formula support.
You can type or paste data directly, fill σ columns automatically, generate data ranges, or enter simple formulas such as =2*x+1.

Opening the data sheet

Choose File → Edit Data
The above table will appear with columns labelled:

X_Data
Y_Data
σY
σX (only visible when x-errors are enabled)

Entering and editing values

You can:

Type directly into any cell.
Double-click to edit an existing value.
Press Enter/Return to confirm and move down one row.
Move horizontally using Tab or Shift+Tab.

Using formulas

Any cell can begin with “=” to indicate a formula.
For example:

=2*x+1
=sin(x)
=sqrt(y)

Formulas can reference column names (x, y, sy, sx) and use standard mathematical functions (sin, cos, tan, exp, log, log10, sqrt, etc.).
When a formula is entered, CFTool evaluates it automatically, using values from the reference column

Note: Once the data sheet has been saved and returned to the main window, any formulas used to create the data will not be stored.

Fill Down

To copy a formula down to lower cells, select the source cell and the cells you wish to update, or select the entire column. Use Ctrl+D (or Cmd+D on macOS) or Right-click → Fill Down” to copy the formula from the top selected cell down the column.

You can mix typed numbers and formulas — CFTool automatically stores both as valid numeric data where possible.

Copying and pasting blocks

You can paste directly from Excel®, LibreOffice, or any tab/comma-separated text.

Select the top-left cell where you want the pasted block to start.
Press Ctrl+V / Cmd+V or Right-click → Paste Selection.
The block replaces existing cells below and to the right of the anchor.

Pasted data can contain one up to four columns; extra columns are ignored.

Copying:
Select a region or column header → Ctrl+C / Cmd+C or Right-click → Copy.

Context menu options

Right-click the table for these quick actions:

Paste Selection – paste from clipboard starting at the selected cell
Copy Selection – copy highlighted cells
Clear Selection – erase selected cells.
Fill down – copy top cell down the selected area (or full column)
Recalculate – recalculated formulas if source column has changed.
Edit formula – If a formula has been used in a cell, it can be edited after evaluation.
Convert data – this section allows you to convert a column to its decimal or natural logarithm or to reverse this conversion.

Auto-fill tools (right-hand panel)

Auto Fill Sigma – the x or y-sigma column with a constant value for all values (as entered in the text box “n”) or with a value equal to “n” multiplied by the corresponding x or y value. You can also fill with the square root of the corresponding x or y value. To choose which sigma column to fill, simply select any box in the target column (only necessary in four column mode). Alternatively, you can create a formula as above.
Auto Fill Range – automatically fill a column with a numerical sequence. Select the top cell of the sequence and set Start, End, and Step, then Apply. For descending sequences, use a negative step
Swap x and y data – this button allows swapping of the values in these two columns.

Managing rows

Buttons below the table:

Add Row – append one blank line to the bottom of the table.
Insert Row – insert a blank line above the currently selected row.
Delete Row – remove the selected line.

Clearing and saving

Right-click → Clear Selection – clears the selected cells.
Save Data – saves the current data sheet as a text file, or returns data to a project.
Save Data As – writes to a new text file, with a new file name, leaving any previously saved file unchanged.

Keyboard shortcuts

Action	Windows/Linux	macOS
Paste	Ctrl+V	Cmd+V
Copy	Ctrl+C	Cmd+C
Fill down (duplicate / apply formula)	Ctrl+D	Cmd+D
Confirm edit / move down	Enter	Return

Tips & notes

Formula columns can be updated if you change dependent values.
Paste anchor matters: pastes always start at the active top-left cell.
To discard changes, simply close the form with the window close button (X).

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